JP2004245584A - Two-terminal circuit element measuring equipment and contact checking method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide two-terminal circuit element measuring equipment for precisely checking contact without being affected by offset capacity, or the like even if capacity in DUTs decreases. <P>SOLUTION: In the measuring equipment, one end of a coaxial cable comprising a first central conductor and a second conductor provided at the outer periphery of the first conductor is connected, and the DUTs are connected to the first conductor at the other end of the cable for checking the contact with the DUTs. The measuring equipment comprises an ammeter that is connected to the DUTs in series via the coaxial cable while a common line is connected to the second conductor of the coaxial cable; a DC voltage generation circuit that is independent of the ammeter, and generates a DC voltage superposed by an AC voltage for applying to the DUTs; and a signal processing means for extracting a DC component and an AC component from the output of the ammeter for obtaining the insulating resistance and AC impedance of the DUTs, and for checking contact accordingly. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit element measuring apparatus, and more particularly, to a contact check method for checking a connection between a sample to be measured (DUT) and a circuit element measuring apparatus, and a two-terminal circuit element measuring apparatus.
[0002]
[Prior art]
With the miniaturization of chip-shaped passive components, the reliability of probing has become a problem even in the automatic inspection process of component manufacturers. For this reason, a circuit element measuring device used in an automatic inspection process of a chip component is provided with a contact check function for checking a connection with an object to be measured.
[0003]
In normal resistance measurement, four-terminal measurement is used, which is not affected by the resistance (lead resistance) of the lead wire. However, two-terminal measurement is used in high-resistance measurement where the lead resistance can be ignored. ing.
A typical sample for high resistance measurement is a capacitor. The higher the insulation resistance of a capacitor, the better it is. However, even if the measuring device and the capacitor have a poor contact, if the measuring device cannot determine that the contact is bad, the capacitor is determined to be high insulation and a good product.
[0004]
In order to solve this problem, there has conventionally been a method of preventing the erroneous measurement due to a contact failure by measuring the AC impedance of the DUT together with the insulation resistance measurement (see Patent Document 1).
[0005]
FIG. 4 shows an example of such a two-terminal circuit element measuring device with a contact check function. In FIG. 4, 4 is a circuit element measuring device, 5 is a triaxial coaxial cable, 6 is a DUT, 7 is an inductor, 8 is a capacitor, 12 is a DC ammeter, 13 is a DC voltage generating circuit, 22 is an AC ammeter, and 23 Is an AC voltage source, 24 is an AC voltmeter, and 41 is a ferrite core transformer.
[0006]
The inductor 7 connected in series, the DC ammeter 12 and the capacitor 8 and the AC ammeter 22 are connected in parallel with each other, and further connected in series to the DUT 6. A DC voltage superimposed on the AC voltage is applied to them by the AC voltage source 23 via the DC voltage generating circuit 13 and the ferrite core transformer 41.
[0007]
The insulation resistance of the DUT 6 is obtained by measuring the value of the known DC voltage generation circuit 13 and the DC component of the flowing current with the DC ammeter 12. On the other hand, the capacity of the DUT 6 is obtained by measuring the voltage applied to the ferrite core transformer 41 with the AC voltmeter 24 and measuring the AC component of the flowing current with the AC ammeter 22.
[0008]
Here, the inductance of the inductor 7 is set sufficiently larger than the impedance of the DUT at the measurement frequency, and the capacitance of the capacitor 8 is set sufficiently smaller than the impedance of the DUT at the measurement frequency.
[0009]
The result of the contact check is determined to be a contact failure when the measured values of the DC ammeter 12 and the AC ammeter 22 are both 0, and when the measured value of the AC ammeter 22 is not 0, the DUT 6 and the measuring device 4 The connection is determined to be normal.
[0010]
4, reference numeral 50 denotes an output resistance of the AC voltage source 23, reference numerals 51 and 55 denote operational amplifiers, reference numerals 52 and 56 denote impedances for current / voltage conversion (I / V conversion), and reference numerals 53 and 57 denote A / D converters.
[0011]
The AC voltage applied to the primary side of the ferrite core transformer 41 (the side to which the AC voltage source 23 is applied) depends on the excitation impedance of the ferrite core transformer 41, the impedance of the DUT 6, and the output impedance 50 of the AC voltage source 23. Therefore, it is necessary to measure directly with the AC voltmeter 24.
[0012]
The DC ammeter 12 includes an I / V converter using an operational amplifier (hereinafter referred to as an operational amplifier) 51, an impedance 52, and an A / D converter 53. The reference potential of these circuits is the potential of the common line 54.
As the operational amplifier 51, a high-precision operational amplifier having small fluctuations in bias current and offset voltage is used. The impedance 52 has a high impedance with respect to DC because it converts a minute DC current into a voltage.
[0013]
In general, precision operational amplifiers are not wideband. Therefore, it is necessary to limit the band with the impedance 52 so as to operate stably with respect to the input capacitance of the DUT. In the device described in Japanese Patent No. 3155310 of Patent Document 1, the DC ammeter 12 cannot obtain a sufficient feedback effect in a band of several hundred kHz, and cannot operate as an ammeter.
[0014]
On the other hand, the AC ammeter 22 includes an I / V converter including an operational amplifier 55 and an impedance 56 and an A / D converter 57, like the DC ammeter 12. As the operational amplifier 55, a high-speed and wide-band operational amplifier is used to cope with a high frequency.
[0015]
However, such a conventional apparatus has the following problems because an AC voltage is applied by a ferrite core transformer.
(1) The excitation impedance of the ferrite core transformer becomes a load on the AC voltage source, and therefore needs to be increased to some extent. To this end, the number of turns on the primary side is increased to increase the inductance, or the frequency is increased to increase the impedance. However, the former requires a larger structure, and the latter requires that peripheral circuits be adapted to higher frequencies.
[0016]
In the device described in Patent Document 1, the latter is selected, and an excitation impedance of several tens Ω is obtained at a frequency of several hundred kHz. However, in an operational amplifier that constitutes an ammeter, there is a trade-off relationship between high accuracy and high bandwidth. Therefore, a DC ammeter that requires accuracy and an AC ammeter that requires high bandwidth are illustrated in the patent of the patent. As shown in FIG. 1, it must be realized by a separate circuit. Therefore, the circuit scale is increased, and the cost is increased.
[0017]
(2) The AC voltage applied to the primary side fluctuates due to the output resistance of the AC voltage source, the excitation impedance of the primary side of the ferrite core transformer, and the secondary side load (DUT). For this reason, in the device described in Japanese Patent No. 3155310, an AC voltmeter is prepared to measure the voltage on the primary side. Therefore, the circuit scale is increased, and the cost is increased.
[0018]
(3) In order to obtain a stable excitation voltage, the first and second conductors of the triaxial coaxial cable must be fixed so as to be located at the center of the ferrite core transformer. Therefore, there is a structural instability factor with respect to the accuracy of the contact check.
[0019]
Japanese Patent Application No. 2002-172257 proposed by the present applicant describes a two-terminal circuit element measuring device that solves such a problem. FIG. 5 is a configuration diagram showing one embodiment.
[0020]
In FIG. 5, reference numeral 4 denotes a main body of the two-terminal circuit element measuring device. 5 is a triaxial coaxial cable, 6 is a DUT, 13 is a DC voltage generating circuit, 23 is an AC voltage source, 60 is an ammeter, 61 is a high-precision operational amplifier, 62 is a capacitor for measuring AC current, and 63 is for measuring DC current. A resistor, 64 is an A / D converter, 65 is a CPU, and 66 is a memory in which a program of the CPU is stored.
[0021]
The ammeter 60 and the DUT 6 are connected in series, and a DC voltage on which an AC voltage is superimposed by an AC voltage source 23 and a DC voltage generating circuit 13 is applied to them.
The insulation resistance of the DUT 6 is obtained by measuring the value of the known DC voltage generating circuit 13 and the DC component of the flowing current with the ammeter 60 and the CPU 65. On the other hand, the AC impedance of the DUT 6 is similarly obtained by measuring the value of the known AC voltage source 23 and the AC component of the flowing current with the ammeter 60 and the CPU 65.
[0022]
The reference for these circuits is 54 potentials. The extraction of the DC component is obtained by passing the output data of the A / D converter 64 through digital signal processing by the CPU 65, specifically, a low-pass filter. The extraction of the AC component is obtained by taking the difference from the case where the DUT is not connected (open state) after passing through the high-pass filter.
[0023]
The program is stored in the memory 66. As a result of the contact check, if the measured values of the DC component and the AC component of the current are both 0, it is determined that the contact is poor. If the measured value of the AC component is not 0, the connection state between the DUT 6 and the measuring device 4 is normal. Is determined.
[0024]
The AC voltage source 23 is set to a frequency at which the high-precision operational amplifier 61 can sufficiently operate as an I / V converter, for example, 10 kHz. At such a frequency, the impedance of the capacitor 62 is set to be sufficiently smaller than the resistance 63, and the impedance of the conductor 62 is set to be sufficiently larger than the resistance 63 at DC. Therefore, DC / AC can be measured by one high-precision operational amplifier.
[0025]
In this measurement, it is possible to perform a contact check without receiving cable capacity by using a triaxial coaxial cable for connection with the DUT and guarding with the second conductor.
[0026]
[Patent Document 1]
Japanese Patent No. 3155310 [FIG. 2 (A)]
[0027]
[Problems to be solved by the invention]
However, this two-terminal circuit element measuring device has the following problems.
(1) As shown in FIG. 6 (a detailed view of the portion A in FIG. 5), the offset capacitance 1 interposed around the jig for fixing the DUT 6 is connected in parallel with the DUT 6. In order to prevent the offset capacitance from affecting the AC impedance measurement, it is necessary to compensate by taking the difference between when the connection between the DUT and the measuring device is in the open state, and a problem may occur when the capacitance of the DUT becomes small. There is.
(2) A triaxial coaxial cable and a connector are required, which causes an increase in cost.
[0028]
An object of the present invention is to solve the above-mentioned problem, and to provide a two-terminal circuit element measuring device capable of performing a contact check with high accuracy without being affected by an offset capacitance or the like even if the capacitance of a DUT becomes small. It is in.
Another object of the present invention is to realize a two-terminal circuit element measuring device that uses a two-axis coaxial cable and a connector without using a three-axis coaxial cable and a connector, thereby reducing costs.
Still another object of the present invention is to realize a two-terminal circuit element measurement device in which a measurement system is floating.
[0029]
[Means for Solving the Problems]
In order to achieve such an object, according to the first aspect of the present invention, one end of a two-axis coaxial cable including a first conductor as a center conductor and a second conductor provided on the outer periphery of the first conductor is connected. A DUT is connected to a first conductor at the other end of the cable, and a measurement device configured to perform a contact check with the DUT,
An ammeter connected in series with the DUT via the biaxial coaxial cable and having a common line connected to a second conductor of the biaxial coaxial cable;
A DC voltage generating circuit for generating a DC voltage on which an AC voltage is superimposed, for applying to the DUT,
Signal processing means for extracting a DC component and an AC component from an output of the ammeter to obtain an insulation resistance and an AC impedance of the DUT, and performing a contact check based on the obtained components.
[0030]
According to such a configuration, the frequency of the AC voltage can be reduced, so that the DC ammeter and the AC ammeter can be realized by the same circuit. Further, since a measurement system can be constructed with a two-axis coaxial cable and a connector for the same without using a three-axis coaxial cable and a connector for the same, the configuration can be made at a low cost. Further, since a floating measurement system can be constructed with respect to ground and the guarded second conductor can be grounded, it can be used with a coaxial cable.
[0031]
In this case, in the ammeter, an inverting input terminal is connected to a first conductor of the coaxial cable, a non-inverting input terminal is connected to a second conductor of the coaxial cable, and It comprises an operational amplifier connected in parallel with a capacitor and a resistor, and an A / D converter for digitally converting the output of the operational amplifier.
[0032]
According to a third aspect of the present invention, one end of a coaxial cable including a first conductor serving as a center conductor and a second conductor provided on the outer periphery of the first conductor is connected to the first conductor at the other end of the cable. Is a measuring device to which a DUT is connected and which can be checked for contact with the DUT.
An ammeter connected in series with the DUT via the coaxial cable and having a common line connected to a second conductor of the coaxial cable;
A DC voltage generation circuit that is a circuit independent of the ammeter and that can selectively generate only a DC voltage or a DC voltage on which an AC voltage is superimposed for application to the DUT;
A signal processing means for extracting a DC component and an AC component from the output of the ammeter to obtain an insulation resistance and an AC impedance of the DUT, and performing a contact check based on the obtained components.
The insulation resistance measurement of the DUT performed by generating only DC from the DC voltage generation circuit and the AC impedance measurement of the DUT performed by generating a DC voltage on which an AC voltage is superimposed are performed at different timings. And
[0033]
According to such a configuration, the DC voltage generating circuit selectively applies the DC voltage or the DC voltage on which the AC voltage is superimposed to the DUT at a shifted timing, thereby increasing the insulation resistance having an extremely high AC impedance. It can be measured with high accuracy.
[0034]
Further, if the common line is grounded at the time of measurement as in claim 4, the influence of the offset capacitance around the jig of the DUT does not reach the ammeter, and the contact check can be performed accurately even with a DUT having a small capacitance.
[0035]
The invention of the contact check method of claim 5 is as follows.
A contact check method for detecting a connection state between a DUT and a measuring device using the two-terminal circuit element measuring device according to claim 1,
If the measured values of the DC component and the AC component of the current obtained by the ammeter and the signal processing unit are both 0, it is determined that the connection is normal, and if the measured value of the AC component is not 0, the connection is determined to be normal. It is characterized by the following.
According to such a method, an accurate contact check can be easily performed.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of a two-terminal circuit element measuring device according to the present invention. In FIG. 1, basically the same components as those in FIG. 5 are given the same numbers. In the figure, 4 is a two-terminal circuit element measuring device, 5 is a two-axis coaxial cable (hereinafter also simply referred to as a coaxial cable), and 6 is a DUT. Reference numeral 60 denotes an ammeter, which comprises a high-precision operational amplifier 61, an AC current measuring capacitor 62, a DC current measuring resistor 63, and an A / D converter 64.
[0037]
65 is a CPU, and 66 is a memory in which a program of the CPU is stored. Reference numeral 70 denotes a DC voltage generation circuit, which includes an AC voltage source 71, a DC voltage source 72, an operational amplifier 73, and resistors 74 to 76.
[0038]
The coaxial cable 5 is formed of a first conductor that is a center conductor and a second conductor provided on the outer periphery of the first conductor. The first conductor at one end is connected to the DUT, and the second conductor at the other end. One conductor is connected to the inverting input terminal of the operational amplifier 61 of the ammeter, and the second conductor is connected to the non-inverting input terminal of the operational amplifier 61.
The second conductor of the coaxial cable 5 is connected to the ground potential on the DUT side.
[0039]
The DUT 6 is connected in series, and the DC voltage of the DC voltage generation circuit 70 is applied to the DUT 6. The DC voltage output from the DC voltage generation circuit 70 is a DC voltage on which the AC voltage from the AC voltage source 71 is superimposed.
[0040]
The insulation resistance of the DUT 6 is obtained by measuring the value of the known DC voltage generating circuit 70 and the DC component of the flowing current with the ammeter 60 and the CPU 65. On the other hand, the AC impedance of the DUT 6 is similarly obtained by measuring the value of the known AC voltage source 71 and the AC component of the flowing current with the ammeter 60 and the CPU 65.
The reference of these circuits is the potential of the common line 54. This potential is common to the common line of the DC voltage generation circuit 70, and is floating with respect to the ground.
[0041]
As a result of the contact check, if the measured values of the DC component and the AC component of the current are both 0, it is determined that the contact is defective. If the measured value of the AC component is not 0, the DUT 6, the measuring device 4, the DC voltage generation circuit It is determined that the connection state of 70 is normal.
[0042]
In this measurement system, when the common line 54 of the measurement device 4 is connected to the ground potential as shown in FIG. 2 (detailed view of the portion B in FIG. 1), both ends of the offset capacitance 1 around the jig for fixing the DUT 6 are operational amplifiers. This is the voltage at the input terminal 61 and no potential difference occurs. Therefore, the offset capacitance 1 does not affect the measurement system. Therefore, the contact check can be accurately performed even for the low-capacity DUT 6 without performing the open correction.
[0043]
Also, since the guarding is grounded, a triaxial coaxial cable or connector is not required, and the coaxial cable and connector can be used.
Since the common line 54 is grounded at one place, there is no influence on the measurement system due to the ground loop.
[0044]
The present invention is not limited to the above-described embodiment, but includes many more changes and modifications without departing from the essence thereof.
For example, the configuration shown in FIG. FIG. 3 is different from FIG. The AC component of the output of the operational amplifier 61 is determined by the capacitance ratio between the DUT 6 and the capacitor 62. Therefore, the output of the operational amplifier 61 saturates depending on the capacitance value of the DUT 6 to be connected, but when the connection with the DUT 6 is not normal, the output of the operational amplifier 61 tends to become 0, which affects the determination of the contact check. Absent.
[0045]
However, if the output of the operational amplifier 61 is saturated, the measurement of the insulation resistance is hindered. Therefore, the switch 65 is opened and closed by the CPU 65 to perform the AC impedance measurement and the insulation resistance measurement at different timings. That is, the switch 71 is opened when measuring the AC impedance, and the switch 71 is closed when measuring the insulation resistance. The contact check is performed based on the respective measurement results in the same manner as described above.
According to such a measurement method, insulation resistance measurement, which is a measurement of very high impedance, can be performed with high accuracy.
[0046]
【The invention's effect】
As described above, the present invention has the following effects.
(1) By setting the common line of the ammeter to the ground potential, the influence of the offset capacitance around the jig can be eliminated, and accurate contact check can be performed even when the capacitance of the DUT is low.
(2) Since the frequency of the AC voltage can be reduced, a DC ammeter and an AC ammeter can be realized by the same circuit.
[0047]
(3) A measuring system can be constructed with a two-axis coaxial cable and a connector for it without using a three-axis coaxial cable and a connector for the same as in the conventional apparatus, which leads to cost reduction.
(4) A floating measurement system can be constructed with respect to ground, and the guarded second conductor can be grounded, so that it can be used with a biaxial coaxial cable.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing one embodiment of a two-terminal circuit element measuring device according to the present invention.
FIG. 2 is a diagram for explaining an influence of an offset capacitance on a measurement system.
FIG. 3 is a configuration diagram showing another embodiment of the present invention.
FIG. 4 is a configuration diagram showing an example of a conventional two-terminal circuit element measuring device.
FIG. 5 is a configuration diagram showing an example of another conventional two-terminal circuit element measuring device.
FIG. 6 is a diagram for explaining the effect of the offset capacitance in FIG. 5 on a measurement system.
[Explanation of symbols]
Reference Signs List 1 offset capacitance 4 two-terminal circuit element measuring device 5 two-axis coaxial cable 6 DUT
54 common line 60 ammeter 61 operational amplifier 62 capacitor 63 resistor 64 A / D converter 65 CPU
66 Memory 70 DC voltage generating circuit 71 AC voltage source 72 DC voltage source 73 Operational amplifier 74 to 76 Resistance 81 Switch

Claims (5)

One end of a biaxial coaxial cable composed of a first conductor as a center conductor and a second conductor provided on the outer periphery of the first conductor is connected, and a DUT is connected to the first conductor at the other end of the cable. , A measuring device configured to perform a contact check with a DUT,
An ammeter connected in series with the DUT via the biaxial coaxial cable and having a common line connected to a second conductor of the biaxial coaxial cable;
A DC voltage generating circuit for generating a DC voltage on which an AC voltage is superimposed, for applying to the DUT,
A two-terminal circuit element measuring device, comprising: a signal processing unit that extracts a DC component and an AC component from an output of the ammeter to obtain an insulation resistance and an AC impedance of the DUT and performs a contact check based on the obtained components. apparatus. The ammeter has an inverting input terminal connected to a first conductor of the biaxial coaxial cable, a noninverting input terminal connected to a second conductor of the biaxial coaxial cable, and a capacitor connected in parallel to a feedback path. 2. The two-terminal circuit element measuring device according to claim 1, further comprising an operational amplifier connected to a resistor, and an A / D converter for digitally converting an output of the operational amplifier. One end of a biaxial coaxial cable composed of a first conductor as a center conductor and a second conductor provided on the outer periphery of the first conductor is connected, and a DUT is connected to the first conductor at the other end of the cable. , A measuring device configured to perform a contact check with a DUT,
An ammeter connected in series with the DUT via the biaxial coaxial cable and having a common line connected to a second conductor of the biaxial coaxial cable;
A DC voltage generation circuit that is a circuit independent of the ammeter and that can selectively generate only a DC voltage or a DC voltage on which an AC voltage is superimposed for application to the DUT;
A signal processing means for extracting a DC component and an AC component from the output of the ammeter to obtain an insulation resistance and an AC impedance of the DUT, and performing a contact check based on the obtained components.
The insulation resistance measurement of the DUT performed by generating only DC from the DC voltage generation circuit and the AC impedance measurement of the DUT performed by generating a DC voltage on which an AC voltage is superimposed are performed at different timings. Two-terminal circuit element measuring device. 4. The two-terminal circuit element measuring device according to claim 1, wherein a common line of the ammeter is grounded. A contact check method for detecting a connection state between a DUT and a measuring device using the two-terminal circuit element measuring device according to claim 1,
If the measured values of the DC component and the AC component of the current obtained by the ammeter and the signal processing unit are both 0, it is determined that the connection is normal, and if the measured value of the AC component is not 0, the connection is determined to be normal. A contact check method, characterized in that:

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